The focus of the proposal is in the area of dosimetry for photodynamic therapy (PDT), especially for breast cancer treatment. It is crucial that the optimal dosage of the three PDT components - photosensitizer, light fluence, and oxygen - be involved for the successful outcome of the treatment. While under dosing can lead to recurrence of the cancer, over dosing can lead to undesirable healthy-tissue damage. A widely accepted method for accurate dosimetry is based on the fact that the quantity of cytotoxic nascent oxygen generated locally during PDT is directly correlated to the treatment outcome. Diffuse optical tomography (DOT) using near infrared light has been used successfully for functional imaging of breast tumors based on their endogenous and exogenous spectral contrast compared to healthy tissue. We will use this well- established DOT technique to perform real-time spatial mapping of nascent oxygen concentration based on the luminescence from the photosensitizer under light fluence. During Phase I, we will develop a detection methodology to demonstrate that the photosensitizer time dependent luminescence characteristics are directly correlated to PDT outcome. Based on the results of Phase I, we will develop a prototype of the spatial nascent oxygen imaging module during Phase II, which will have parallel acquisition across a cooled multi-detector array for high resolution and high throughput imaging. The low-cost, compact PDT dosimetric imager module will be designed to be compatible with existing DOT systems to extend their applications for monitoring during PDT for breast and other cancer treatments. PUBLIC HEALTH RELEVANCE: Diffuse luminescence imaging can be used to obtain quantitative spatial maps of nascent oxygen concentration based on time domain characteristics of the drugs used in photodynamic therapy (PDT). PDT following breast lumpectomy to prevent local recurrence of cancer is the primary target application, with the goal of improving treatment outcome and minimizing side effects. Other applications could include monitoring for dose evaluation during PDT treatments in brain cancers, head and neck cancers, and other non-cancerous conditions.